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Tissue kallikrein permits early renal adaptation to potassium load.

El Moghrabi, Soumaya; Houillier, Pascal; Picard, Nicolas; Sohet, Fabien; Wootla, Bharath; Bloch-Faure, May; Leviel, Françoise; Cheval, Lydie; Frische, Sebastian; Meneton, Pierre; Eladari, Dominique; Chambrey, Régine.
Proc Natl Acad Sci U S A; 107(30): 13526-31, 2010 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-20624970
Tissue kallikrein (TK) is a serine protease synthetized in renal tubular cells located upstream from the collecting duct where renal potassium balance is regulated. Because secretion of TK is promoted by K+ intake, we hypothesized that this enzyme might regulate plasma K+ concentration ([K+]). We showed in wild-type mice that renal K+ and TK excretion increase in parallel after a single meal, representing an acute K+ load, whereas aldosterone secretion is not modified. Using aldosterone synthase-deficient mice, we confirmed that the control of TK secretion is aldosterone-independent. Mice with TK gene disruption (TK-/-) were used to assess the impact of the enzyme on plasma [K+]. A single large feeding did not lead to any significant change in plasma [K+] in TK+/+, whereas TK-/- mice became hyperkalemic. We next examined the impact of TK disruption on K+ transport in isolated cortical collecting ducts (CCDs) microperfused in vitro. We found that CCDs isolated from TK-/- mice exhibit net transepithelial K+ absorption because of abnormal activation of the colonic H+,K+-ATPase in the intercalated cells. Finally, in CCDs isolated from TK-/- mice and microperfused in vitro, the addition of TK to the perfusate but not to the peritubular bath caused a 70% inhibition of H+,K+-ATPase activity. In conclusion, we have identified the serine protease TK as a unique kalliuretic factor that protects against hyperkalemia after a dietary K+ load.
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